During the year ended December 31, 2020, the Company granted awards under the 2018 Omnibus Incentive Compensation Plan, previously named the Amended and Restated 2009 Omnibus Incentive Compensation Plan (the “2018 Plan”), and the 2015 Incentive Compensation Plan (the “2015 Plan”). The Compensation Committee of the Board of Directors administers the plans.

During the year ended December 31, 2019, the Board approved and transferred all available shares from the 2015 Plan to the 2018 Plan. Under the 2018 Plan, a maximum of 8,897,084 shares of common stock may be issued upon the exercise of stock options, in the form of restricted stock, or in settlement of RSUs or other awards, including awards with alternative vesting schedules such as performance-based criteria.

For the years ended December 31, 2020 and 2019, the following table presents total share-based compensation expense in each functional line item on the consolidated statements of operations (in thousands):


	Year Ended December 31,
	2020		2019
Cost of revenues	$	1,583	$	1,133
Research and development	2,823		1,548
Sales and marketing	2,346		1,669
General and administrative	3,667		2,952

Total	$	10,419	$	7,302

The Compensation Committee of the Board of Directors determines eligibility, vesting schedules and exercise prices for stock options granted. Stock options generally have a term of ten years and vest over a three- to four-year period.

The following table presents the weighted-average assumptions used in the Black-Scholes valuation model by the Company in calculating the fair value of each stock option granted:


	Year Ended December 31,
	2020		2019
Expected dividend yield	—	%	—	%
Risk-free interest rate	0.9	%	1.8	%
Volatility	95	%	81	%
Expected term (in years)	5.8		5.8

The weighted-average fair value of stock option awards granted during the years ended December 31, 2020 and 2019 was $7.11 and $3.56, respectively.

The following table summarizes the Company’s stock option activity for the years ended December 31, 2020 and 2019 (dollars in thousands, except per share data):


	Stock Options Outstanding	Weighted-Average Exercise Price Per Option		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value




Outstanding — December 31, 2019	9,044,304	$	2.91
Granted	1,526,000	9.41
Exercised	(1,357,620)	3.06
Canceled	(732,705)	3.60
Outstanding — December 31, 2020	8,479,979	$	3.99	7.47	$	97,315
Vested and Expected to Vest — December 31, 2020	7,667,800	$	3.71	7.34	$	90,150
Exercisable — December 31, 2020	4,293,975	$	2.10	6.41	$	57,398

During the year ended December 31, 2019, 1,489,067 shares were issued upon the exercise of stock options. The total intrinsic value of stock options exercised to purchase common stock during the years ended December 31, 2020 and 2019 was approximately $11.7 million and $5.6 million, respectively.

As of December 31, 2020, total unrecognized share-based compensation expense related to non-vested stock options was $12.3 million, which is expected to be recognized over a weighted-average period of approximately 2.5 years. The Company recognized approximately $5.8 million and $3.5 million of share-based compensation expense related to the vesting of stock option awards during the years ended December 31, 2020 and 2019, respectively.

Pursuant to the 2018 Plan and the 2015 Plan, the Company may issue RSUs that, upon satisfaction of vesting conditions, allow recipients to receive common stock. Issuances of such awards reduce common stock available under the 2018 Plan and 2015 Plan for stock incentive awards. The Company measures compensation cost associated with grants of RSUs at fair value, which is generally the closing price of the Company’s stock on the date of grant. RSUs generally vest over a three- to four-year period.

A summary of restricted stock unit activity under all plans for the year ended December 31, 2020 is presented below:


	Number of Shares	Weighted-Average Grant-Date Fair Value
Non-vested — December 31, 2019	400,315	$	3.95
Granted	570,368	10.52
Vested	(548,160)	7.28
Forfeited	(5,418)	4.06
Non-vested — December 31, 2020	417,105	$	8.68

During the year ended December 31, 2019, the weighted-average grant-date fair value of RSUs granted was $5.07. During the years ended December 31, 2020 and 2019, the total fair value of shares vested was $5.1 million and $4.0 million, respectively.

As of December 31, 2020, there was $1.8 million of unrecognized share-based compensation expense related to non-vested RSUs, which is expected to be recognized over a weighted-average period of 2.2 years. The Company recognized approximately $4.1 million and $3.5 million of share-based compensation expense related to the vesting of RSUs during the years ended December 31, 2020 and 2019, respectively.

The ESPP permits eligible employees of the Company to purchase newly issued shares of common stock, at a price equal to 85% of the lower of the fair market value on (i) the first day of the offering period or (ii) the last day of each six-month purchase period, through payroll deductions of up to 10% of their annual cash compensation. Under the ESPP, a maximum of 5,324,000 shares of common stock may be purchased by eligible employees.

During the years ended December 31, 2020 and 2019, the Company issued 231,275 shares and 203,061 shares, respectively, under the ESPP. The Company recognized approximately $0.6 million and $0.3 million of share-based compensation expense related to the ESPP during the years ended December 31, 2020 and 2019, respectively.